In the vehicle braking systems currently in production, there is no way to detect while using the vehicle, if not by means of external systems, the forces that are exchanged between the brake pads (or brake shoes for vehicles still equipped with drum brakes) and the element to be braked, disc or drum, that is attached to the wheel. This makes it impossible to detect and/or predict the occurrence of many drawbacks which can vary from abnormal brake pad wear due for example to the pads “touching” the disc even when braking is not taking place due for example to a wrong caliper adjustment, rather than the noise, vibration and undesirable squealing while braking. These problems can lead to malfunctions or even to premature and often unnecessary brake pad replacement.
KR2004-48957A attempts to solve the problem of the generation of noise and vibration during braking by arranging piezoelectric elements behind the metal support for the brake pad which is known as the “backplate”. These piezoelectric elements, as a result of the vibrations to which the backplate is subjected during use, generate electric energy which is subsequently dissipated by supplying said energy to LEDs. By absorbing energy in this manner these vibrations are dampened.
More generally the use of piezoelectric elements (sensors or actuators) for experimental purposes is known in the art. For example taking piezoelectric elements and arranging them on the backplate towards the outer edges of the brake caliper in order to detect the deformations of said backplate during braking bench tests or for counteracting the vibrations that are generated during braking by electrically supplying piezoelectric actuators such that these actuators then apply forces to the backplate that should counterbalance and thus dampen the vibrations.
For example, the SAE Technical Paper 2004-01-2773 describes a study conducted by the University of Darmstadt in which piezoelectric elements are coupled together with acceleration sensors and used both as sensors and actuators for the suppression of squealing during braking. The same study points out however that the system described should be considered as a design aid tool and not as a system suitable for use in the mass production of brake pads.
It should be noted in fact that at the moment it is considered to be extremely difficult, if not impossible, to have piezoelectric sensors in the vicinity of brake pads or on the brake pads themselves, both due to the high temperatures and pressures to which brake pads are subjected during the production process, or that are developed during braking, and to the evident construction difficulties associated with a system that should effectively function in an efficient and reliable way.